Contemporary aircraft include fans used for various cooling purposes, which currently include a configuration having two grease-packed bearings that support a rotating shaft of the fan. Due to a harsh operational environment of high temperature and high rotational speeds, the grease forming the bearing lubricant deteriorates quickly, resulting in relatively frequent maintenance to keep the fan in operating condition. The maintenance is currently done by completely removing at least a portion of the fan from the aircraft, which is expensive and time consuming.
In U.S. Patent Application Publication No. 2014/0044524 a fan that utilizes oil for shaft bearing lubrication instead of grease is described. The integrated screw pump within the shaft circulates oil in a vertical orientation for bearing lubrication and allows the fluid to be changed without removing the impeller fan assembly from the aircraft. The casing of the pump allows for swirling of the lubrication fluid, which can prevent the pump from achieving maximum effectiveness. Using a separate lubricating pump and plumbing system could complicate the fan mechanism and increase cost.